


Once in a Full Moon

by CMeister



Category: Free!
Genre: Domestic Fluff, Full Moon, Gift Exchange, M/M, Romance, alternative universe, mermaid, merman
Language: English
Status: Completed
Published: 2019-01-09
Updated: 2019-01-09
Packaged: 2019-10-07 10:11:49
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,080
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17364044
Author URL: https://archiveofourown.org/users/CMeister/pseuds/CMeister
Summary: It was that time of the month again. It seemed like the months were passing much faster than they used to, or maybe it was like that old saying, times goes by faster when you’re having fun. And Ikuya was having fun, not that he would ever admit it aloud. Until Hiyori's time of the month decides to throw a wrench into Ikuya's comfortable daily routine.





	Once in a Full Moon

**Author's Note:**

> This is my gift to @prismaticposse (twitter) for the Dive to the New Year Twitter event. It was my first time participating in such an event and posting a fic so please enjoy!!
> 
> Huge shout out to Yuu (@nakimochin on twitter) for beta reading!

It was that time of the month again. It seemed like the months were passing much faster than they used to, or maybe it was like that old saying, times goes by faster when you’re having fun. And Ikuya was having fun, not that he would ever admit it aloud. 

His daily life had settled down into a comfortable routine of classes, swim practice, work at his part-time job at Nao’s café, a little bit of extra training if he was up to it, and then spending a quiet evening with Hiyori, who would usually get home just before Ikuya finished his extra training. They would make dinner together and chat about their day. 

It was comfortable. 

Until something threw a wrench into Ikuya’s comfortable daily routine. 

“Ikuya!” The door to the bathroom slams open as the older Kirishma enters dramatically, grocery bags in hand. “Are you done getting things ready in here?”

The bathroom was the only part of the tiny two bedroom apartment that Ikuya and Hiyori splurged on. They went with a mermaid theme with calm blue walls and ceramic floor tiles in various shades of blue and green. They kept the furnishings to a minimum, a white quartz countertop with two sinks mounted above light espresso colored cabinets finished with satin nickel hardware. 

And the best part of the bathroom, having both a shower and a bath tub. 

“Almost.” Ikuya says scrubbing away at the hard metal residue on the side of the tub. “Thanks for helping, Hiyori’s change started earlier than usual.”

Natsuya leaves the bags on the floor and hoists himself carefully onto the bathroom counter, his long legs knocking into the cabinet doors. “He didn’t say anything to you about it?” 

Ikuya shakes his head, his frustration fueling his scrubbing. When your boyfriend is part merfolk, you tend to get used to their quirks and interesting habits. Many island nations were home to large populations of merfolk of all types. Most merfolk that needed to be constantly near a source of water could be found in large port cities along the coast fishing, diving for food throughout the year while some rarely interacted with humans, preferring to inhabit hard to reach caverns near cliffs and by dangerous reefs, calling out warnings to sailors if they ever got too close. And of course there were merfolk like Hiyori and Nao, merfolk whose blood has intermixed with humans enough to live out of water for long periods of time. They are human in all aspects with the exception of being able to breath under water and their time of the month when their legs turn back to tails under the full moon. 

What didn’t help in the situation is when said boyfriend decides to hide his early transformation until he collapses due to fatigue and needs to be sent home from practice, putting Ikuya in a state of constant anxiety. 

“Well, I’m sure he has his own reasons.” Natsuya says giving Ikuya a pointed stare clearly telling Ikuya to go and talk to Hiyori. Which was easy for Natsuya to say, Nao wasn’t the type of hide things and put his health at risk. Sure they had their differences, but Nao always confided in Natsuya on private matters. 

Ikuya finally decides that the tub isn’t going to get any cleaner than it already is and drains the soapy water. He could smell something delicious wafting through the air. With all the last minute preparations he had to do, Ikuya hadn’t noticed that it was well into the afternoon now. “Thanks for your help, I’m sure you have to get going soon.”

Natsuya claps a firm hand on Ikuya’s back. “It’s fine. We’re happy to help. Nao really appreciates all the help with setting up his café.” He steers them down the hall where the aforementioned silver haired merman was setting the table with plates of omelet rice, cute little ketchup swirls decorating the tops of the fluffy egg. 

“I made some porridge for Hiyori.” Nao says indicating to the tray on the kitchen counter. “Why don’t you go see if he’s up?” 

“Thank you.” Ikuya graciously picks up the tray, careful to not spill anything as he walks down the hall to their shared bedroom. Despite choosing a two bedroom apartment, Ikuya and Hiyori made the mutual decision to make one a study room and the other just for sleeping and lounging. Which was how they were able to fit a large queen sized bed in the bedroom. 

Ikuya knocks on the door, listening for any sign that Hiyori might be awake. He hears a soft mumble, and pushes open the door. Hiyori had gathered all the blankets to his side of the bed, making a nest of sorts out of the soft layers. He pokes his disheveled head out from under the blankets, squinting in the darkness. “Ikuya?” 

“Nao made some porridge.” Ikuya says softly, sitting at the edge of the bed by the Hiyori shaped lump, balancing the tray on his lap. Hiyori squirms out of the blankets until he’s half sitting and half laying on the bed. He still looks tired, despite sleeping most of the day. Hiyori takes the tray and slowly eats the porridge. “Do you want to get in the tub?”

Hiyori pauses for a moment. “I can wait until you’re not busy.” 

Ikuya frowns at Hiyori. “I want to take care of you when you’re not feeling well.” He says softly, staring down the frayed edges of some of the older blankets in the pile. He is suddenly very interested in counting the number of stray threads. 

Ikuya can feel Hiyori’s stare boring into him, and it is making Ikuya’s blush creep across his cheeks and up to his ears. He knew that Hiyori didn’t like being taken care of, but somethings couldn’t be helped and Ikuya wanted to be there for Hiyori during those times. 

“Then, I would like to get in the tub soon.” Hiyori says equally as soft, his spoon scrapping at the bottom of the bowl. 

“Ok.” Ikuya smiles. “Let me go get it ready.” He can hear Natsuya and Nao bickering at each other in the dining room and knew they wouldn’t notice his missing presence for a while longer. 

Ikuya turns on the bathroom light and begins to fill the newly cleaned bathtub with hot water. He fills it up most of the way before turning on the cold water. As the tub fills, Ikuya rummages through the grocery bags for the mersalt Natsuya promised to buy earlier. 

Mersalt was a certain ratio of minerals that were typically found in seawater and nutrients to keep the energy of merfolk up during their transformation periods. It has become a must-have in modern society due to the merfolk population spanning across the nation with many not having direct access to seawater. 

Ikuya quickly reads the instructions for the mersalt and tears open the bag. The concentrated salty concoction almost burns his sinuses as small powdery residue explode into the air. He uses the designated scooper to measure out the proper amount and swirls it into the water, it bubbles and sizzles a bit before dissolving into the water. 

The temperature is getting close to Hiyori’s preference so Ikuya turns off the faucets and goes to get his boyfriend. It secretly makes Ikuya really happy to be able to call Hiyori _his boyfriend_. Even after all this time, Ikuya still gets small little flutters in his stomach when he thinks about it and every once in a while Hiyori would catch him smiling and ask why. Ikuya would never admit it, but he is absolutely convinced that Hiyori is made of all sorts of wonderful. 

Hiyori is still in the same half sitting half laying down position that he was in when Ikuya left him. “All ready.” Ikuya announces, indicating for Hiyori to get out of his blanket burrito, which he does reluctantly. 

It seems like getting lethargic and weak when out of water are common indicators that a merfolk’s monthly transformation is nearing. Hiyori also tends to crave more sweets when they go grocery shopping and his coffee orders also has extra syrup in them during this period. 

Hiyori shuffles slowly to the bathroom. Ikuya makes sure that Hiyori makes it into the bathroom before taking the empty dish back to the kitchen. Natsuya and Nao are done eating and were chatting around some cups of coffee no doubt from Hiyori’s personal stash. 

“How’s he doing?” Natsuya asks when Ikuya makes his presence known to the other couple. 

“Better.” Ikuya says setting the dish in the sink, he could wash it later. His stomach is grumbling for food and the omlette rice is still looking really good. “I got him into the tub, so I’ll check on him in a bit.”

Nao scoots the plate over to the empty seat at the table for Ikuya. He doesn’t have to be told twice, he mumbles a quick thanks and immediately dives into the dish. The rice inside is still warm, and spicy. Nao’s taste tends to veer towards the spicy side, which Ikuya doesn’t really mind. It was never spicy enough that he couldn’t eat it, but he knew it drove Natsuya crazy sometimes. 

“I left some other dishes in the fridge.” Nao says once Ikuya is done inhaling his lunch. “Make sure to remember to eat.” 

Ikuya thanks them again, making sure to see them off properly before returning his attention to his merboyfriend. Hiyori is sitting in the bathtub, his tail hanging over the edge of the tub, staring dazedly at the opposite wall. “Feeling better?”

Hiyori nods, swishing the water back and forth. He looks more refreshed and the color is starting to come back to his face. Ikuya walks over to the small cabinet and picks up a set of scrubbing brushes. He sits on the edge of the tub by Hiyori’s tail and starts gently scrubbing the scales. 

“You don’t have to.” Hiyori says immediately trying to move out of Ikuya’s reach. 

“I want to.” Ikuya says making sure to give Hiyori his firmest look. Hiyori scoots his tail back towards Ikuya. They sit in silence, the sound of scrubbing echoing around them. 

Ikuya admires the glittery iridescent shine of the scales. Hiyori’s scales are a gorgeous deep teal with a golden tinge to them. When they catch the light just right, he could see rainbows in them. It is a sight that Ikuya never gets tired of seeing. 

The teal contrasts beautifully with the slightly paler purple in Hiyori’s fins. Ikuya could see the mesmerizing flow of the fins on Hiyori’s arms as Hiyori continues to play with the water. “You’re really cute.” Hiyori says suddenly. 

Sometimes Hiyori says the oddest things. “You’re really weird.” Ikuya retorts. Hiyori smiles, his gills bubbling under the surface of the water. Any unsettling feelings from the morning are immediately washed away. 

“Ah, I need to send an email to my professors.” Hiyori says breaking out of the moment. 

Ikuya is once again thankful that their university is rather open and understanding of merfolks. Their training schedules are planned to allow for a week off every month and the training centers are always stocked with merfolk medication that are otherwise difficult to obtain. 

“I’ll go get your bag.” Ikuya says, putting the brushes back in the cabinet. Their study room is minimalistic. Both of them have a simple desk and office chair set up on opposite walls with a pair of bookshelves on the wall facing the door. Ikuya’s desk had all of his class materials organized neatly in different piles and shelves. His bookshelf was mainly used to hold sentimental objects, a few childhood pictures and swimming trophies, his old copy of the Little Mermaid, and some souvenirs from Natsuya. 

Hiyori’s desk is mostly bare, he preferred to do all his school work at cafes or the university library. And his bookshelf held actual books. Books on nutrition, cooking, history, coffee, and various other topics Ikuya had no clue why Hiyori had books on. Ikuya grabs Hiyori’s bag off his desk chair, all of his school material and laptop are still packed inside. 

After a brief pause, Ikuya also grabs his own bag and makes his way back across the hall to the bathroom. Hiyori pops his head out from under the water when Ikuya walks back into the bathroom. He sets the bags down next to the tub and gets the bath tray out from under the sink for Hiyori to set up on. “How’s your work load?” 

“The usual.” Hiyori says sinking a bit back into the water. His gills spread open, the water bubbling as they take in and expel the saltwater. “The new coach is tough, but nothing I can’t handle. My research paper isn’t due for a few more days and I’ll put in a request of absence for that class.” 

Despite both entering the same university for swimming, they hardly ever saw each other. The merfolk had their own sport’s facility with trainers and coaches specifically for merfolk athletes. They are also in different departments, Linguistics and Journalism for Hiyori and Sports Business for Ikuya, which meant they are in different buildings for all their classes. 

But they always meet up in the cafeteria for lunch and they often have joint practices. Plus, by living together this year, they are able to spend morning and evenings together. And it also meant that Hiyori didn’t have to spend his time of the month alone either. 

Ikuya smiles at Hiyori’s content face. “Nao made some food for us, do you want to eat or drink anything? Coffee?”

“Just coffee, please!” Hiyori says folding his arms over the edge of the tub, his head propped on top of them innocently. 

“Yes, my princess.” Ikuya drawls leaving the bathroom quickly, his blush is already creeping up to his ears. He started using that nickname in retaliation for when Hiyori referred to him as ‘cute’ but saying those words usually resulted in both of them blushing to their hairlines. 

In the kitchen, Ikuya takes a quick inventory of the food Nao left in the fridge. Despite it being almost evening time, he isn’t hungry so he opts to just make Hiyori’s coffee. Ikuya goes over to the cabinets and pulls out Hiyori’s pour over dripper and his favorite mug. 

Hiyori is a coffee snob. He has been using his journalism major to fuel his coffee café blog. If there’s one thing to know about Hiyori, it’s that he likes coffee, and he likes his coffee made in a certain way. Ground coffee beans, freshly grounded with each brew, hot water poured just before boiling point, and it has to be poured in a slow circular motion into the mug underneath. Ikuya, on the otherhand, could never discern the difference between coffee made with fresh coffee beans and instant coffee, which was blasphemous according to Hiyori but coffee was coffee to Ikuya. But since it matters to Hiyori, Ikuya painstakingly learned the nuances to the perfect cup of coffee. He adds one cube of sugar and a little bit of cream to the mug as well. A quick mix and Ikuya is ready for judgement. 

“Thanks for the coffee.” Hiyori already has his laptop set up, his fingers rapidly moving across the keyboard. He moves the laptop to the side and graciously takes the mug from Ikuya. Ikuya watches Hiyori carefully as he takes a few sips, his tail gently swishing in delight. “Your coffee is improving. It’s good.” 

Ikuya releases the breath he didn’t realize he had been holding. “Of course, who do you think taught me?” He huffs dramatically. 

Hiyori blinks at him like Ikuya’s made of all types of wonderful “you’re so cute,” he says easily. Ikuya pouts, a blush spreading across his cheeks. Hiyori easily goes back to drinking his coffee as if he hadn’t just said something embarrassing. 

Ikuya settles back on the stool, pulling out his laptop as well. They easily settle into their usual light conversations. Ikuya complaining about doing his entire group project by himself and preparing to roast his groupmates on the final peer review. And Hiyori is basking in the glow of his blog getting more and more attention over the past three months. His journalism degree going to good use.  
Quiet tapping echo throughout the bathroom as they both focus in on the tasks in front of them. It’s late into the night by the time Ikuya looks up from the mess that’s his group project. He stretches his arms above his head, a horrifying number of cracks popping from his back. 

“You should head to sleep, Ikuya.” Hiyori says, glancing up from his screen. “It’s already really late and you have practice tomorrow.” 

Ikuya hums in agreement, doing one last save before closing his laptop down for the night. He’s too tired to think about going to class tomorrow. He’s so wrapped up in his own thoughts, he doesn’t notice the slightly mischievous smile that graces Hiyori’s lips. 

Just as Ikuya is about to say good night, Hiyori flicks him with his shimmery teal tail, splashing salty water into Ikuya’s face. Ikuya sputters at the sudden wetness, wiping water from his eyes.  
“You’re such a—“he starts, but Hiyori reaches up out of the water and grabs him by the collar of his shirt, planting a soft kiss on his lips. Ikuya’s pretty sure his brain short circuits at the sudden initiation of intimacy. Hiyori takes the moment to wrap one arm around Ikuya’s waist while the other pushes his tray to the other end of the tub and pulls Ikuya into the tub. 

The lukewarm water jolts Ikuya back to life. Hiyori’s chuckling at Ikuya, mumbling something along the lines of ‘cute’ again. Ikuya rolls his eyes, brushing his dripping bangs out of his eyes. Normally he would have hated getting his casual clothes wet, but he could care less at the moment. Below him is his beloved merman, golden eyes shining with laughter and pure joy. A rare sight. 

Ikuya moves to straddle Hiyori’s waist, leaning down so his lips are hovering just above Hiyori’s. “I love you.” Ikuya takes in the awe-struck look in Hiyori’s eyes before planting a soft kiss on Hiyori’s soft, salty lips.

Sometimes it’s nice to break out of their comfortable daily routines.


End file.
